Energetic Investment Research Articles

Paternal energetic investments in copepods

Copepod mating is a complex behavioral interplay between males and females. But successful mating also requires a physiological component in terms of egg- and spermatophore production. In striking contrast to the extensive literature on copepod egg production, costs of spermatophore production has largely been ignored. This article explores the energetic demands in male copepod reproduction, testing how food and predation risk influence spermatophore production. Moreover, we analyse swimming behavior to test if predation risk and food act on reproductive investments via behavioral responses. We found that spermatophore production depends strongly on food availability. The copepods increased grazing rates with predation risk when food was limited, and video analyses revealed that males spend less time swimming in presence of a risk cue. A review of the few available spermatophore production rates suggests that food limits spermatophore production for copepods at large. Apparently, potential encounter rates with mates or predators did not influence spermatophore production. However, the reduced activity indicates a trade-off between risk avoidance and mate encounter, potentially influencing mating rates. This study shows that males invest considerable resources in each spermatophore, with implications for mating strategies and population dynamics in copepods, the most abundant metazoans on earth.

Commentary: Noradrenaline and Dopamine Neurons in the Reward/Effort Trade-off: A Direct Electrophysiological Comparison in Behaving Monkeys.

Commentary: Noradrenaline and Dopamine Neurons in the Reward/Effort Trade-off: A Direct Electrophysiological Comparison in Behaving Monkeys.

Locomotion: Why We Walk the Way We Walk

The way we walk determines the energetic investment needed. Humans spontaneously alter their walking style to exploit energetic opportunities. New research demonstrates the sensitivity and timing of this optimization and opens the door to discovering the underlying mechanisms.

Snake venoms are integrated systems, but abundant venom proteins evolve more rapidly.

BackgroundWhile many studies have shown that extracellular proteins evolve rapidly, how selection acts on them remains poorly understood. We used snake venoms to understand the interaction between ecology, expression level, and evolutionary rate in secreted protein systems. Venomous snakes employ well-integrated systems of proteins and organic constituents to immobilize prey. Venoms are generally optimized to subdue preferred prey more effectively than non-prey, and many venom protein families manifest positive selection and rapid gene family diversification. Although previous studies have illuminated how individual venom protein families evolve, how selection acts on venoms as integrated systems, is unknown.ResultsUsing next-generation transcriptome sequencing and mass spectrometry, we examined microevolution in two pitvipers, allopatrically separated for at least 1.6 million years, and their hybrids. Transcriptomes of parental species had generally similar compositions in regard to protein families, but for a given protein family, the homologs present and concentrations thereof sometimes differed dramatically. For instance, a phospholipase A2 transcript comprising 73.4 % of the Protobothrops elegans transcriptome, was barely present in the P. flavoviridis transcriptome (<0.05 %). Hybrids produced most proteins found in both parental venoms. Protein evolutionary rates were positively correlated with transcriptomic and proteomic abundances, and the most abundant proteins showed positive selection. This pattern holds with the addition of four other published crotaline transcriptomes, from two more genera, and also for the recently published king cobra genome, suggesting that rapid evolution of abundant proteins may be generally true for snake venoms. Looking more broadly at Protobothrops, we show that rapid evolution of the most abundant components is due to positive selection, suggesting an interplay between abundance and adaptation.ConclusionsGiven log-scale differences in toxin abundance, which are likely correlated with biosynthetic costs, we hypothesize that as a result of natural selection, snakes optimize return on energetic investment by producing more of venom proteins that increase their fitness. Natural selection then acts on the additive genetic variance of these components, in proportion to their contributions to overall fitness. Adaptive evolution of venoms may occur most rapidly through changes in expression levels that alter fitness contributions, and thus the strength of selection acting on specific secretome components.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1832-6) contains supplementary material, which is available to authorized users.

Reproduction and immunity trade-offs constrain mating signals and nuptial gift size in a bushcricket

Reproduction and immunity often require significant energetic investment and as a result, trade-offs may occur between them. Reproduction is particularly costly for males of the bushcricket Ephippiger diurnus: not only do they produce loud advertisement calls for long periods of time to attract mates but also they offer females a large nuptial gift, a spermatophore, that can be up to 40% of their body weight. Song traits and spermatophore size vary among males, implying that males may differ in their overall reproductive effort or in how their effort is allocated. Males are long-lived, suggesting that survival traits such as immunity may be particularly critical in fitness. Here, we tested the hypothesis that trade-offs exist between reproductive effort and immune response in E. diurnus and that such trade-offs may constrain male mating calls and nuptial gift size. We investigated the relationship between call syllable number, spermatophore size, and immune response in field-collected individuals. We found an inverse relationship in all pairwise comparisons of call syllable number, spermatophore size, and immune response, as well as between overall reproductive effort and immune response. Our results suggest that males exhibit different energy allocation strategies and that their trade-offs ultimately constrain signal evolution.

A dynamic energy budget for the whole life‐cycle of holometabolous insects

Alterations of the amount and quality of food consumed during ontogeny can affect different life‐history traits, such as growth rate, developmental time, survival, adult size, and fitness. Understanding the dynamics of such metabolic and energetic pathways and investments is particularly challenging in the case of holometabolous insects due to their strikingly different life stages. We show how whole life‐cycle energy and mass budgets can be achieved for holometabolic insects through dynamic energy budget (DEB) theory, permitting the fate of acquired and stored nutrients to be followed over a complete life‐cycle. We applied the DEB theory to model the whole life‐cycle energetics of an endoparasitic wasp, Venturia canescens (Hymenoptera: Ichneumonidae). Data on embryo, larval, and pupal dry mass, imago longevity, and fecundity were used for assessing the goodness of fit of the model. Our model predicted the growth curves of the larval and pupal stages, the number of eggs laid by the imago through time, and lifespan events, such as the different developmental times of the parasitoid. The model enabled us to distinguish and follow the energy invested in eggs through income and capital reserves. The mechanisms leading to the double costs of being small (a shorter life under starving conditions and fewer eggs) were identified by running the model for varying amounts of food eaten early in life, according to host sizes. The final larval instar harvests around 60 times the energy of a recently hatched larva. Around 90% of this energy is then used during pupation to build the structure of the imago and to pay maintenance. Imagoes, therefore, emerge with only a small percentage of the energy stored by the last instar larvae. Our study shows that, despite being small, this percentage of energy stored during the parasitoid development has a great impact on adult fitness, the loss of which cannot be compensated for by a rich adult environment. Our model is generic and has applications for a wide range of applied and theoretical questions about insect energetics, from population dynamics in multitrophic systems to responses to climate change and life‐history strategies.

Detoxification mechanisms of honey bees (Apis mellifera) resulting in tolerance of dietary nicotine.

Insecticides are thought to be among the major factors contributing to current declines in bee populations. However, detoxification mechanisms in healthy, unstressed honey bees are poorly characterised. Alkaloids are naturally encountered in pollen and nectar, and we used nicotine as a model compound to identify the mechanisms involved in detoxification processes in honey bees. Nicotine and neonicotinoids have similar modes of action in insects. Our metabolomic and proteomic analyses show active detoxification of nicotine in bees, associated with increased energetic investment and also antioxidant and heat shock responses. The increased energetic investment is significant in view of the interactions of pesticides with diseases such as Nosema spp which cause energetic stress and possible malnutrition. Understanding how healthy honey bees process dietary toxins under unstressed conditions will help clarify how pesticides, alone or in synergy with other stress factors, lead to declines in bee vitality.

Extracellular haem peroxidases mediate Mn(II) oxidation in a marine Roseobacter bacterium via superoxide production.

Manganese (Mn) oxides are among the strongest sorbents and oxidants in environmental systems. A number of biotic and abiotic pathways induce the oxidation of Mn(II) to Mn oxides. Here, we use a combination of proteomic analyses and activity assays, to identify the enzyme(s) responsible for extracellular superoxide-mediated Mn oxide formation by a bacterium within the ubiquitous Roseobacter clade. We show that animal haem peroxidases (AHPs) located on the outer membrane and within the secretome are responsible for Mn(II) oxidation. These novel peroxidases have previously been implicated in direct Mn(II) oxidation by phylogenetically diverse bacteria. Yet, we show that in this Roseobacter species, AHPs mediate Mn(II) oxidation not through a direct reaction but by producing superoxide and likely also by degrading hydrogen peroxide. These findings point to a eukaryotic-like oscillatory oxidative-peroxidative enzymatic cycle by these AHPs that leads to Mn oxide formation by this organism. AHP expression appears unaffected by Mn(II), yet the large energetic investment required to produce and secrete these enzymes points to an as yet unknown physiological function. These findings are further evidence that bacterial peroxidases and secreted enzymes, in general, are unappreciated controls on the cycling of metals and reactive oxygen species (ROS), and by extension carbon, in natural systems.

Trait variability of the signal crayfish (Pacifastacus leniusculus) in a recently invaded region reflects potential benefits and trade-offs during dispersal

Rapid range expansion is one of the major attributes of invasion success. During range expansion, dispersing individuals face a novel environment where trade-offs between benefits of reduced conspecific density and pressure from niche competitors may differentially affect life-history traits essential for population growth. In this study, we examined differences in sex ratio, body condition, physiological condition and capacity for energetic investment into reproduction along an actively expanding range of one of the most successful crayfish invaders in Europe, the signal crayfish (Pacifastacus leniusculus). In the examined invasive range, signal crayfish faces competition by a native crayfish, Astacus leptodactylus. By comparing measured parameters between invasion fronts and invasion core sites, we analyzed whether the potential benefits of dispersal to areas with low conspecific density are outweighed by the competitive pressure from a native crayfish. Caught signal crayfish of both sexes from invasion fronts were in a better body condition compared to those from the invasion core, while females from invasion fronts also exhibited better energetic status of hepatopancreas and gonads. At the same time, A. leptodactylus from the contact zones at invasion fronts were in poorer body condition compared to those outside the invaded range. Thus, interspecific competition at invasion fronts affected the native A. leptodactylus more strongly than the signal crayfish, which still benefited from the reduced conspecific density in the presence of a competitor. This study highlights the importance of examining trait variability as invader advances its range, since a shift between the rate of population growth and counteracting pressure from other niche competitors could represent one of the crucial determinants of a lag between establishment and expansion of invasive species.

Does predation risk affect mating behavior? An experimental test in dumpling squid (Euprymna tasmanica).

IntroductionOne of the most important trade-offs for many animals is that between survival and reproduction. This is particularly apparent when mating increases the risk of predation, either by increasing conspicuousness, reducing mobility or inhibiting an individual's ability to detect predators. Individuals may mitigate the risk of predation by altering their reproductive behavior (e.g. increasing anti-predator responses to reduce conspicuousness). The degree to which individuals modulate their reproductive behavior in relation to predation risk is difficult to predict because both the optimal investment in current and future reproduction (due to life-history strategies) and level of predation risk may differ between the sexes and among species. Here, we investigate the effect of increased predation risk on the reproductive behavior of dumpling squid (Euprymna tasmanica).ResultsFemales, but not males, showed a substantial increase in the number of inks (an anti-predator behavior) before mating commenced in the presence of a predator (sand flathead Platycephalus bassensis). However, predation risk did not affect copulation duration, the likelihood of mating, female anti-predator behavior during or after mating or male anti-predator behavior at any time.ConclusionsInking is a common anti-predator defense in cephalopods, thought to act like a smokescreen, decoy or distraction. Female dumpling squid are probably using this form of defense in response to the increase in predation risk prior to mating. Conversely, males were undeterred by the increase in predation risk. A lack of change in these variables may occur if the benefit of completing mating outweighs the risk of predation. Prioritizing current reproduction, even under predation risk, can occur when the chance of future reproduction is low, there is substantial energetic investment into mating, or the potential fitness payoffs of mating are high.

The link between immunity and life history traits in scleractinian corals.

Immunity is an important biological trait that influences the survival of individuals and the fitness of a species. Immune defenses are costly and likely compete for energy with other life-history traits, such as reproduction and growth, affecting the overall fitness of a species. Competition among these traits in scleractinian corals could influence the dynamics and structural integrity of coral reef communities. Due to variability in biological traits within populations and across species, it is likely that coral colonies within population/species adjust their immune system to the available resources. In corals, the innate immune system is composed of various pathways. The immune system components can be assessed in the absence (constitutive levels) and/or presence of stressors/pathogens (immune response). Comparisons of the constitutive levels of three immune pathways (melanin synthesis, antioxidant and antimicrobial) of closely related species of Scleractinian corals allowed to determine the link between immunity and reproduction and colony growth. First, we explored differences in constitutive immunity among closely related coral species of the genus Meandrina with different reproductive patterns (gonochoric vs. hermaphrodite). We then compared fast-growing branching vs. slow-growing massive Porites to test co-variation between constitutive immunity and growth rates and morphology in corals. Results indicate that there seems to be a relationship between constitutive immunity and sexual pattern with gonochoric species showing significantly higher levels of immunity than hermaphrodites. Therefore, gonochoric species maybe better suited to resist infections and overcome stressors. Constitutive immunity varied in relation with growth rates and colony morphology, but each species showed contrasting trends within the studied immune pathways. Fast-growing branching species appear to invest more in relatively low cost pathways of the immune system than slow-growing massive species. In corals, energetic investments in life-history traits such as reproduction and growth rate (higher energy investment) seem to have a significant impact on their capacity to respond to stressors, including infectious diseases and coral bleaching. These differences in energy investment are critical in the light of the recent environmental challenges linked to global climate change affecting these organisms. Understanding physiological trade-offs, especially those involving the immune system, will improve our understanding as to how corals could/will respond and survive in future adverse environmental conditions associated with climate change.

Basal metabolic rate and maternal energetic investment durations in mammals.

BackgroundThe Metabolic Theory of Ecology (MTE) predicts that gestation duration, lactation duration, and their sum, total development time, are constrained by mass-specific basal metabolic rate such that they should scale with body mass with an exponent of 0.25. However, tests of the MTE’s predictions have yielded mixed results. In an effort to resolve this uncertainty, we used phylogenetically-controlled regression to investigate the allometries of gestation duration, lactation duration, and total development time in four well-studied mammalian orders, Artiodactyla, Carnivora, Primates, and Rodentia.ResultsThe results we obtained are not consistent with the predictions of the MTE. Gestation duration scaling exponents are below 0.25 in all four orders. The scaling exponent for lactation duration is below 0.25 in Carnivora and Rodentia, indistinguishable from 0.25 in Artiodactyls, and steeper than 0.25 in Primates. Total development time scales with body mass as predicted by the MTE in Primates, but not in artiodactyls, carnivores, and rodents. In the latter three orders, the exponent is 0.15.ConclusionsTogether, these results indicate that the influence of basal metabolic rate on mammalian maternal investment durations must be more complicated than the MTE envisages, and that other factors must play an important role. Future research needs to allow for the possibility that different factors drive gestation duration and lactation duration, and that the drivers of the two durations may differ among orders.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0194-z) contains supplementary material, which is available to authorized users.

Energetic optimisation of foraging honeybees: flexible change of strategies in response to environmental challenges.

Heterothermic insects like honeybees, foraging in a variable environment, face the challenge of keeping their body temperature high to enable immediate flight and to promote fast exploitation of resources. Because of their small size they have to cope with an enormous heat loss and, therefore, high costs of thermoregulation. This calls for energetic optimisation which may be achieved by different strategies. An ‘economizing’ strategy would be to reduce energetic investment whenever possible, for example by using external heat from the sun for thermoregulation. An ‘investment-guided’ strategy, by contrast, would be to invest additional heat production or external heat gain to optimize physiological parameters like body temperature which promise increased energetic returns. Here we show how honeybees balance these strategies in response to changes of their local microclimate. In a novel approach of simultaneous measurement of respiration and body temperature foragers displayed a flexible strategy of thermoregulatory and energetic management. While foraging in shade on an artificial flower they did not save energy with increasing ambient temperature as expected but acted according to an ‘investment-guided’ strategy, keeping the energy turnover at a high level (∼56–69 mW). This increased thorax temperature and speeded up foraging as ambient temperature increased. Solar heat was invested to increase thorax temperature at low ambient temperature (‘investment-guided’ strategy) but to save energy at high temperature (‘economizing’ strategy), leading to energy savings per stay of ∼18–76% in sunshine. This flexible economic strategy minimized costs of foraging, and optimized energetic efficiency in response to broad variation of environmental conditions.

The cost of being queen: Investment across Pogonomyrmex harvester ant gynes that differ in degree of claustrality

The role of the ant colony largely consists of non-reproductive tasks, such as foraging, tending brood, and defense. However, workers are vitally linked to reproduction through their provisioning of sexual offspring, which are produced annually to mate and initiate new colonies. Gynes (future queens) have size-associated variation in colony founding strategy (claustrality), with each strategy requiring different energetic investments from their natal colony. We compared the per capita production cost required for semi-claustral, facultative, and claustral gynes across four species of Pogonomyrmex harvester ants. We found that the claustral founding strategy is markedly expensive, costing approximately 70% more energy than that of the semi-claustral strategy. Relative to males, claustral gynes also had the largest differential investment and smallest size variation. We applied these investment costs to a model by Brown and Bonhoeffer (2003) that predicts founding strategy based on investment cost and foraging survivorship. The model predicts that non-claustral foundresses must survive the foraging period with a probability of 30–36% in order for a foraging strategy to be selectively favored. These results highlight the importance of incorporating resource investment at the colony level when investigating the evolution of colony founding strategies in ants.

Mapping the conformational space accessible to catechol-O-methyltransferase.

Methylation catalysed by catechol-O-methyltransferase (COMT) is the main pathway of catechol neurotransmitter deactivation in the prefrontal cortex. Low levels of this class of neurotransmitters are held to be causative of diseases such as schizophrenia, depression and Parkinson's disease. Inhibition of COMT may increase neurotransmitter levels, thus offering a route for treatment. Structure-based drug design hitherto seems to be based on the closed enzyme conformation. Here, a set of apo, semi-holo, holo and Michaelis form crystal structures are described that define the conformational space available to COMT and that include likely intermediates along the catalytic pathway. Domain swaps and sizeable loop movements around the active site testify to the flexibility of this enzyme, rendering COMT a difficult drug target. The low affinity of the co-substrate S-adenosylmethionine and the large conformational changes involved during catalysis highlight significant energetic investment to achieve the closed conformation. Since each conformation of COMT is a bona fide target for inhibitors, other states than the closed conformation may be promising to address. Crystallographic data for an alternative avenue of COMT inhibition, i.e. locking of the apo state by an inhibitor, are presented. The set of COMT structures may prove to be useful for the development of novel classes of inhibitors.

The tubular compartment and the spermatogenic dynamics of the wild rodent Oxymycterus nasutus (Rodentia: Cricetidae)

Despite the order Rodentia present worldwide distribution and large number of species in the Brazilian fauna, detailed studies on testicular morphophysiology are still scarce. Therefore, this study aimed to analyze the dynamics of the spermatogenic process of Oxymycterus nasutus using morphometrical and stereological tools. Testicles from ten sexually mature males were used, showing a gonadosomatic index of 0.89%. The testicular parenchyma showed one of the highest tubulesomatic indexes reported among wild rodents – 0.82% – from which 65.12% was allocated into seminiferous epithelium. The average tubular diameter was 249.89μm, whereas the epithelium height was 62.47μm and the total length was 18.62m per gram of testis. Eight different stages of the seminiferous epithelium cycle were described. Stage 1 was used for counting the germ cell population as well as the Sertoli cells. On average, 3.47 type-A spermatogonia, 24.39 primary spermatocytes in preleptotene/leptotene, 24.13 primary spermatocytes in pachytene, 68.38 round spermatids and 7.33 Sertoli cells were found per tubular cross section. There were 91.02×106 Sertoli cells per gram of testis and each cell was able to support 9.33 spermatids and 16.43 germ cells. The coefficient of spermatogonial mitosis was 7.02, while 2.83 spermatids were produced for each primary spermatocyte in pachytene. The overall efficiency of spermatogenesis was 19.70 cells, whereas the sperm reserve per gram of testis totalized 849.63×106 spermatids. Therefore, the presented data showed that O. nasutus shows a high energetic investment in reproduction, corroborating the findings for other species of the Cricetidae family.

Evidence of multiple paternity and cooperative parental care in the so called monogamous silver arowana Osteoglossum bicirrhosum (Osteoglossiformes: Osteoglossidae)

Monogamy is rare in fishes and is usually associated with elaborate parental care. When parental care is present in fishes, it is usually the male that is responsible, and it is believed that there is a relationship between the high energetic investment and the certainty of paternity (except in the case of sneaker males). Osteoglossum bicirrhosum is considered a monogamous fish, and has particular behavioral traits that permit the study of mating systems and parental care, such as male mouthbrooding. We investigated the genetic relationships of males with the broods found in their oral cavities in Osteoglossum samples collected in a natural environment in the lower Purus river basin, Amazonas, Brazil. Fourteen broods were analyzed for parentage (268 young and 14 adult males) using eight microsatellite loci. The results indicate that eleven broods show a monogamous system. In one brood, however, approximately 50% of the young were genetically compatible with being offspring of another male, and in another two broods, none of the subsampled young were compatible with the genotypes of the brooding male. The result of this first brood may be explained by the extra-parental contribution of a sneaker male, whereas cooperative parental care may explain the result in the other two broods.

Effects of Extrinsic Mortality on the Evolution of Aging: A Stochastic Modeling Approach

The evolutionary theories of aging are useful for gaining insights into the complex mechanisms underlying senescence. Classical theories argue that high levels of extrinsic mortality should select for the evolution of shorter lifespans and earlier peak fertility. Non-classical theories, in contrast, posit that an increase in extrinsic mortality could select for the evolution of longer lifespans. Although numerous studies support the classical paradigm, recent data challenge classical predictions, finding that high extrinsic mortality can select for the evolution of longer lifespans. To further elucidate the role of extrinsic mortality in the evolution of aging, we implemented a stochastic, agent-based, computational model. We used a simulated annealing optimization approach to predict which model parameters predispose populations to evolve longer or shorter lifespans in response to increased levels of predation. We report that longer lifespans evolved in the presence of rising predation if the cost of mating is relatively high and if energy is available in excess. Conversely, we found that dramatically shorter lifespans evolved when mating costs were relatively low and food was relatively scarce. We also analyzed the effects of increased predation on various parameters related to density dependence and energy allocation. Longer and shorter lifespans were accompanied by increased and decreased investments of energy into somatic maintenance, respectively. Similarly, earlier and later maturation ages were accompanied by increased and decreased energetic investments into early fecundity, respectively. Higher predation significantly decreased the total population size, enlarged the shared resource pool, and redistributed energy reserves for mature individuals. These results both corroborate and refine classical predictions, demonstrating a population-level trade-off between longevity and fecundity and identifying conditions that produce both classical and non-classical lifespan effects.

Can we afford storage? A dynamic net energy analysis of renewable electricity generation supported by energy storage

Global wind power and photovoltaic (PV) installed capacities are growing at very high rates (20% per year and 60% per year, respectively). These technologies require large, ‘up-front’ energetic investments. Conceptually, as these industries grow, some proportion of their electrical output is ‘re-invested’ to support manufacture and deployment of new generation capacity. As variable and intermittent, renewable generation capacity increases grid penetration, electrical energy storage will become an ever more important load-balancing technology. These storage technologies are currently expensive and energy intensive to deploy. We explore the impact on net energy production when wind and PV must ‘pay’ the energetic cost of storage deployment. We present the net energy trajectory of these two industries (wind and PV), disaggregated into eight distinct technologies—wind: on-shore and off-shore; PV: single-crystal (sc-), multi-crystalline (mc-), amorphous (a-) and ribbon silicon (Si), cadmium telluride (CdTe), and copper indium gallium (di)selenide (CIGS). The results show that both on-shore and off-shore wind can support the deployment of a very large amount of storage, over 300 hours of geologic storage in the case of on-shore wind. On the other hand, solar PV, which is already energetically expensive compared to wind power, can only ‘afford’ about 24 hours of storage before the industry operates at an energy deficit. The analysis highlights the societal benefits of electricity generation–storage combinations with low energetic costs.

Belowground advantages in construction cost facilitate a cryptic plant invasion.

The energetic cost of plant organ construction is a functional trait that is useful for understanding carbon investment during growth (e.g. the resource acquisition vs. tissue longevity tradeoff), as well as in response to global change factors like elevated CO2 and N. Despite the enormous importance of roots and rhizomes in acquiring soil resources and responding to global change, construction costs have been studied almost exclusively in leaves. We sought to determine how construction costs of aboveground and belowground organs differed between native and introduced lineages of a geographically widely dispersed wetland plant species (Phragmites australis) under varying levels of CO2 and N. We grew plants under ambient and elevated atmospheric CO2, as well as under two levels of soil nitrogen. We determined construction costs for leaves, stems, rhizomes and roots, as well as for whole plants. Across all treatment conditions, the introduced lineage of Phragmites had a 4.3 % lower mean rhizome construction cost than the native. Whole-plant construction costs were also smaller for the introduced lineage, with the largest difference in sample means (3.3 %) occurring under ambient conditions. In having lower rhizome and plant-scale construction costs, the introduced lineage can recoup its investment in tissue construction more quickly, enabling it to generate additional biomass with the same energetic investment. Our results suggest that introduced Phragmites has had an advantageous tissue investment strategy under historic CO2 and N levels, which has facilitated key rhizome processes, such as clonal spread. We recommend that construction costs for multiple organ types be included in future studies of plant carbon economy, especially those investigating global change.